Both Thai and Bama (Thaing/Banshay) martial arts have duel-wield forms.
Here is a video with Banshay double-sword forms (minutes 2:57 and 4:29).
I have not found a matched pair of dha shay/daab, however I have seen matched pairs of dha hmyaung (daggers). My guess is that over the years the sword sets on the market have just gotten broken up, which is a pity. In Thai tradition pairs of daab are worn crossed on the back. I've wondered how a Bama would carry two dha shay, as the traditional way is by a loop over the shoulder, which would be a rather awkward way to carry a pair.